Thrownness names the naked that of existence — the sheer fact that Dasein is, without the why ever being fully available to it. Dasein does not choose its birth, its language, its historical moment, the fundamental moods in which the world is disclosed to it. It finds itself already there, already attuned to a world, already speaking a language that thinks it as much as it thinks in it. The existential counterpart to thrownness is the mood of anxiety, which discloses the groundlessness of this situation: that Dasein is not founded on any deeper ground but simply is, in the way that it is, without ultimate justification.
Moods (Stimmungen) are not psychological states superimposed on a neutral perception of the world. They are prior to perception and constitute it: it is always in some mood that Dasein finds the world disclosed to it in a particular way, with certain things salient and others receding. Boredom levels everything, making the world indifferent. Joy opens up possibilities. Anxiety individualises Dasein, stripping away the comfortable anonymity of das Man and confronting it with its own most possibility. Moods are the way in which Dasein is delivered over to its situation — the primary mode in which it finds how things are.
Facticity does not mean raw, uninterpreted givenness. Dasein's factical situation is always already interpreted — understood through a pre-given tradition of meanings, practices, and self-understandings that constitute what Heidegger calls the "they-self" (das Man). The thrown Dasein inherits an interpretation of itself and its world before it has any opportunity to take a stand on that inheritance. Authentic existence is not the rejection of this inheritance but the explicit appropriation of it — understanding one's throwness as one's own, and owning the possibilities it opens rather than simply drifting within them.
Thrownness and facticity are analysed throughout Division One and Two of Being and Time. Anxiety as the fundamental attunement that discloses thrownness is discussed in §40; the formal structure of care as thrownness-projection-fallenness in §§41–42.
